The invention relates to a pressure-fluid-operated percussion device comprising a frame allowing a tool to be arranged therein movably in its longitudinal direction, means for feeding pressure liquid to the percussion device and for returning pressure liquid to a pressure liquid tank, and means for producing a stress pulse in the tool by utilizing pressure of the pressure liquid, wherein the percussion device comprises a working pressure chamber filled with pressure liquid and, between the working pressure chamber and the tool, a transmission piston which is movably arranged in the longitudinal direction of the frame and which is in contact with the tool either directly or indirectly at least during stress pulse generation, and a charging pressure chamber on the side of the transmission piston facing the tool so that the transmission piston is provided with a pressure surface facing the working pressure chamber and on the side of the charging pressure chamber a pressure surface facing the tool.
In the prior art, in a percussion device a stress pulse in a tool is produced by using a reciprocating percussion piston which, at the end of its stroke movement, hits an end of a tool or a shank connected thereto, thus producing in the tool a stress pulse propagating towards the material to be processed. The reciprocating stroke movement of a percussion piston is typically produced by means of a pressure medium whose pressure makes the percussion piston move in at least one direction, today typically in both directions. In order to enhance the stroke movement, a pressure accumulator or a spring or the like may be utilized to store energy during a return movement.
Due to the reciprocating movement of a percussion piston, acceleration forces in opposite directions are alternately produced in percussion devices equipped with a percussion piston which subject the mechanism to stress and impede control of the percussion device. In addition, due to such forces, boom structures and feeding apparatuses usually employed for supporting a percussion device have to be more robust than would otherwise be necessary. Furthermore, in order to make a stress pulse to be transferred from the tool to the material to be processed, such as rock to be broken, efficiently enough, the percussion device, and hence the tool, have to be pushed against the material with a sufficient force. Due to dynamic acceleration forces, the feed force and structures, accordingly, have to be dimensioned to be robust enough so that the pressing force on the tool which remains as a difference of acceleration caused by the feed force and the movement of the percussion piston would still be sufficiently large. Furthermore, percussion devices equipped with a percussion piston operating by a reciprocating stroke movement are only able to provide low stroke frequencies since to accelerate the percussion piston in its direction of movement always requires an amount of power proportional to the mass of the percussion piston, and high frequencies would require high acceleration and thus extremely high powers. This, in turn, is not feasible in practice, since all the rest in the percussion device and the support structure thereof would have to be dimensioned accordingly. When at the same time this would result in a considerable decrease in efficiency, the stroke frequency of existing percussion devices is only a few dozens of Hz at its best.